The present invention relates to a process for the preparation of racemic diphosphines, to a process for the preparation of enantiomerically pure diphosphines, to novel enantiomerically pure diphosphines, to novel intermediates for the preparation of diphosphines, and to catalysts that contain novel diphosphines.
A process that differs greatly from the process according to the invention for the preparation of diphosphines is known from EP-A 749,973. According to this, if the intention is to prepare enantiomerically pure diphosphines, the racemate resolution is carried out at the stage of the phosphine oxides, i.e., for individual diphosphines separate racemate resolutions must be carried out. Compounds different from the compounds according to the invention are described in EP-A 104,375, EP-A 582,692, and EP-A 690,065. Racemate resolutions with N-benzylcinchonidinium chloride have hitherto been described only for dinaphthol compounds (Tetrahedron Lett. 36, 7991 (1995)).